1. Field of the Invention
This invention relates to electronic optical display devices and methods of manufacturing the same, and more particularly to an electronic optical display device comprising two substrates which are the same in plane configuration and a method fo manufacturing the same.
2. Description of the Prior Art
An electronic optical display device comprising two transparent substrates and an electro-optical substance such as a liquid crystal, electrochromic substance and the like sealed in a gap formed between the substrates has heretofore been well known. In such kind of device, one of the substrates is made larger than the other substrate for the purpose of easily connecting a lead electrode through a connector to a driving circuit.
In an electronic optical display device for a thin type digital watch, it is preferable to make its glass substrate thin. As a result, two glass substrates are adhered together and a liquid crystal is injected and sealed into a gap formed between the two substrates, then one of the substrates is made 0.3 mm in thickness and the total thickness of the two substrates is made 0.6 mm by lapping and polishing working. Such method, however, has the drawback that the lead electrode provided on one of the substrates and projected from the other substrate is liable to be cracked during the working and that a shock resistant property of the display device incorporated into the watch becomes degraded.
That is, in a conventional liquid crystal display device shown in FIGS. 1 and 2 and comprising an upper glass substrate 1, a lower glass substrate 2, a segment type transparent electrode 3, a common transparent electrode 4, a sealing portion 5, a lead electrode 6, a nematic liquid crystal layer 7, an upper light deflecting plate 8, a lower light deflecting plate 9, and a reflecting plate 10, the upper glass substrate 1 is made larger than the lower glass substrate 2 and projected therefrom by a distance which corresponds to the dimension of the lead electrode 6. In FIG. 1 is shown a time displayed on the upper glass substrate for the sake of explanation. Similarly, such time is also displayed on the upper glass substrate shown in the following figures. In order to manufacture the conventional liquid crystal display cell shown in FIGS. 1 and 2, the upper and lower glass substrates adhered together by the sealing portions are subjected to lapping and polishing working so as to make the thickness of the upper and lower glass substrates 1, 2 about 0.3 mm, thereby forming a thin type cell whose overall thickness is about 0.6 mm. In this case, however, there is a risk of that portion of the upper glass substrate which is coated with the lead electrode 6 being broken, thereby rendering the production of the thin type cell in mass production scale difficult.
In addition, in a digital watch which makes use of a conventional electronic display device such as a liquid crystal etc., a windshield of the watch is separated from the glass substrate for the liquid crystal so as to form a space therebetween. Such conventional construction has the drawback that the watch as a whole becomes large in thickness and a thin type digital watch could not be made in practice.
Various kinds of methods of manufacturing the display panel have been proposed. These methods are classified into a method of manufacturing one display panel in which two substrates corresponding to one display panel are worked and then adhered or sealed together and a method of manufacturing a plurality of display panels in which two large types substrates corresponding to a plurality of display panels are worked and then adhered or sealed together to form an assembly and finally the assembly is separated into a plurality of display panels.
The method of manufacturing one display panel is good in yield, but has the disadvantage that successive steps result in one display panel only. In the method of manufacturing a plurality of display panels, it is possible to manufacture a plurality of display panels by successive steps, but the yield thereof is inferior to that of the method of manufacturing one display panel. As seen from the above, both the method of manufacturing one display panel and the method of manufacturing a plurality of display panels have their own drawbacks, respectively.